ارزیابی راهکار های سازگاری نخود دیم (Cicer arietinum L.) به تغییرات اقلیمی آینده در استان زنجان

Introduction
Chickpea (Cicer arietinum L.) is cultivated on alarge scale in arid and semiarid environments. Terminal drought and heat stress, among other abiotic and biotic stresses, are the major constraints of yield in most regions of chickpea production. The study of the effects of climate change could help to develop adaptation strategies to promote and stabilize crop yield. This research was aimed to assess adoption strategies in rainfed chickpea in response to Zanjan province’s climate change using a crop simulation model along with providing simulated yield maps using geographical information system (GIS).
Materials and methods
To study the effects of climate change and simulation the adaptation strategies, the model of Soltani and Sinclair (Soltani & Sinclair, 2011) was used. This model simulates phenological development, leaf development and senescence, mass partitioning, plant nitrogen balance, yield formation and soil water balance. For each location, a baseline period of daily weather data was available (Table 1). Investigated scenarios were historical climate (control) and future climate scenarios that included both direct effects of doubling CO2 (350 to 700 ppm) and its indirect effects (10% reduced rainfall, 4ºC increase in temperature). The crop model was performed for the different years of baseline period for current and future climate under typical management and cultivar and also under three adaptation strategies in the future climate including Management adaptation (M), Genetic adaptation (G) and a combination of both Management and Genetic adaptation (M & G) as described below (Table 2):
Management – In various studies changing the planting dates as the simplest and least-cost adaptation strategy has been emphasized (Luo et al., 2009); hence a shift in planting dates i.e. sowing 15 days in advance was explored in this study to reduce the risk of the late season drought.
Genetics – Changes in genotype have been suggested to be the most promising adaptation option in the world. Earlier maturity cultivars may be needed to match future drier conditions. Thus alternative genotype was a cultivar with 20% lesser of the required biological day from emergence to flowering.
M & G – The third adaptation practice was an attempt to combine both earliness and early sowing date (15 days).
A randomized complete-block design was used for data analysis in which climate condition with considered treatment and years was considered as blocks. When it was necessary, mean comparison was done using a Least Significant Difference (LSD) procedure at 5% level.
Results and discussion
The results showed that in future climatic change, mean yield for Zanjan province will reach to 1036 kg.ha-1 with 38.4% increasing which was statistically different compared to current situation (760 kg.ha-1). The possibilities for gathering more benefits of grain yield were tested by changing traditional management and genetics of the locations in the future climate which involved three management options as adaptation strategies (Earlier Sowing, Earlier maturity Cultivars and combination of these two options). Applying earlier sowing date in comparison with conventional sowing date, increased mean yield by 67.7% (1268 kg.ha-1). In addition, applied earlier maturity cultivar led to 1212 kg.ha-1 (63.9% increase in comparison with current cultivar). Results revealed that using earlier maturity cultivars in combination with earlier sowing date will increase mean yield up to 1452 kg.ha-1 (94.5% increase),whichwasthe consequence of a shift in growing season to a wetter part of the year and reduced the risk of late season drought stress. Furthermore, breeding for earliness by reducing the vegetative period would save more water to be used for grain filling. Under these circumstances, according to decreased environmental risks, yield sustainability will increase up to 28.4%.
Conclusion
The Results of this study can also be extended to water-limited regions of chickpea producing with similar climatic and edaphic conditions. New varieties should be released with shorter growth periods than current ones and their sowing dates must be advanced if possible. Other management practices such as conservation tillage or keeping residue on the soil surface in order to save and increase soil water content were not included in this study which is suggested to evaluate the effects of these factors on the yield of crops in the future climate change studies.